Paranasal sinuses are air containing chambers
surrounding the nasal cavity. Pathology involving the sinuses, may
present on the radiograph as alterations in the translucency of the
sinuses. Some pathological conditions affecting the para nasal
sinuses may produce fluid hence effort should be made to demonstrate
this fluid level. This is possible if the radiograph is taken in
erect position allowing a clear air fluid level to be visualised in
the radiograph.

Standard positions of sinus
radiographs:

Radiographic positions to
study the paranasal sinuses are standardised around three positions:

1. Two anatomical - namely
cornal and sagittal

2. One radiographic - termed
as radiographic base line. This line represents a line drawn from
the outer canthus of the eye to the mid point of the external
auditory canal.

The various radiographic
positions used to study paranasal sinuses are:

1. Occipito-mental view
(Water's view)

2. Occipital-frontal view
(Caldwel view)

3. Submento-vertical position
(Hirtz position)

4. Lateral view

5. Oblique view 39 Degrees
oblique (Rhese position)

Occipito mental view: This is
also known as the Water's view. This is the commonest view taken to
study the paranasal sinuses. The patient is made to sit facing the

radiographic base line tilted
to an angle of 45 degrees to the horizontal making the sagittal
plane vertical. The radiological beam is horizontal and is centered
over a point 1 inch above the external occipital protruberance. In
obese patients with a short neck it is virtually impossible to
obtain an angulation of 45 degrees. These patients must be made to
extend the neck as much as possible and the xray tube is tilted to
compensate for the difference in angulation. The mouth is kept open
and the sphenoid sinus will be visible through the open mouth. If
the radiograph is obtained in a correct position the skull shows a
foreshortened view of the maxillary sinuses, with the petrous apex
bone lying just beneath the floor of the maxillary antrum. In this
view the maxillary sinuses, frontal sinuses and anterior ethmoidal
sinuses are seen. The sphenoid sinus can be seen through the open
mouth.

Diagram showing the position of the skull in water's
view x- ray

If the antrum in water's view
demonstrates a loss of translucency which could be an indicator of
fluid level, then another x ray is taken with a tilt of saggital
plane to an angle of 30 degrees. This view will clearly demonstrate
movement of fluid to a new position. In this view the fluid moves
towards the lateral portion of the antrum where it can clearly be
seen.

Xray
para nasal sinuses (Water's view)
named

Xray
sinus water's view

In x ray para
nasal sinuses waters view the normal frontal sinus margins show
scalloping. Loss of this scalloping is a classic feature of frontal
mucocele. If frontal sinus is congenitally absent (agenisis) then a
suture line known as the metopic suture is visible in the fore head
area. Sometimes a pair of large anterior ethmoidal air cells may
take up the place of frontal sinuses. Here too the metopic suture
line is visible. This suture divides the two halfs of frontal bone
of the skull in infants and children. This suture line usually
disappears at the age of 6 when it fuses. If this suture is not
present at birth it will cause a keel shaped deformity of the skull
(trigonocephaly).

X ray sinuses water's view showing
agenesis of frotal sinuses, along with the presence of metopic
suture. The maxillary antrum are hypoplastic with sclerosed walls.
Hypoplastic antra can be a normal variant.

Since hypoplastic antra are
associated with sclerosis of its margins, it will be very difficult
to perforate the medial wall of the antrum while performing
antrostomy.

Expansion is characterised by
increase in the size of maxillary antrum when compared to its
counter part on the opposite side.

Erosion may occur in the medial
wall of the antrum or in its antero lateral wall. The canine fossa
area is the thinnest portion of maxillary antrum antero lateral
wall. Erosion is hence common in this area.

Opacity is the term used to
describe a maxillary sinus antra involved with malignant growth.
This opacity is due to the periosteal reaction due to malignant
growth.

Occipito frontal view (Caldwell
view): This position is ideally suited for studying frontal sinuses.
In this position the frontal sinuses are in direct contact with the
film hence there is no chance for any distortion or geometric blur
to occur.

Fig
showing the skull position in caldwell
view

To get a caldwell view the
patient is made to sit in front of the film with the radiographic
base line tilted to an angle of 15 - 20 degrees upwards. The
incident beam is horizontal and is centered 1/2 inch below the
external occipital protruberance. This view is also known as the
frontal sinus view.

Submentovertical view: is
primarily taken to demonstrate sphenoid sinuses. Fluid levels in
sphenoid sinuses are clearly shown in this view. To take an x ray in
this position, the back of the patient is arched as far as possible
so that the base of skull is parallel to the film. The x ray beam is
centered in the midline at a point between the angles of the jaws.
In elderly patients this view can be easier to achieve if carried
out in the supine position with the head hanging back over the end
of the table. This view also demonstrates the relative thicknesses
of the bony walls of the antrum and the frontal
sinuses.

Fig
showing the position of the skull in submento vertical
view

Lateral view:

This view helps in distinguishing
the various pathologies involving the frontal sinuses. It helps in
determining whether the loss of translucency is due to thickening of
the anterior bony wall or infection of the frontal sinus per se.
This view also demonstrates fluid levels in the antrum. This view
also gives information on the naso pharynx and soft palate. This is
infact a standard projection used to ascertain enlargement of
adenoid tissue.

Xray
skull lateral view

For this
view the patient is made to sit with the sagittal plane parallel to
the xray film and the radiographic base line is horizontal. The
incident ray is horizontal and the incident beam is centered at the
mid point of the antrum.

Patient
position in lateral view skull

Oblique view:

This view helps in demonstrating
posterior ethmoid air cells and optic foramen. To obtain this
projection the patient is made to sit facing the film. The head is
rotated so that the sagittal plane is tured to an angle of 39
degrees. The radiographic base line is at an angle of 30 degrees to
the horizontal. The incident beam is horizontal and is centered so
that the beam passes through the centre of the orbir nearest to the
film.

With the advent of CAT scan these
modalities of imaging are slowly losing their relevance.